Almost a year and a half ago, the spoke protector on my rear bike wheel finished breaking
I write "finished breaking" because it probably cracked a while back, and started to fall apart way earlier. After a while, I noticed a rattling sound on my 20" wheel and noticed that it had cracked. The crack turned to a fracture, and eventually it was rattling a lot more and I decided to take it off.
Made of clear plastic, they clip onto the spokes of your rear wheel behind the cassette (or they clip onto the flange of your rear hub), and it looks like the tabs had first broken, and then all the extra movement quickened its downfall. The UV light from the sun probably made it brittle too.
Why did I think I needed another spoke guard?
The spoke protector (aka spoke guard, dork disc) protects your spokes in case you shift past the biggest cassette cog and get your chain wedged between the cog and the spokes. It's derogatorily called a "dork disc" because if your bike is properly set up, then you should never have this problem. As long as you set the rear derailleur limit screws correctly, your chain should never jump over the largest cog.
Some people even remove these as soon as they get a bike because they look a little unsightly and they sometimes might feel embarassing to the rider. And they might add a few grams of weight to your ride.
I used to think that too, until I managed to overshift my chain in between my rear wheel's spokes and the cassette. I guess I'd been tuning my rear derailleur and thought I'd set up the limit screw correctly.
I don't remember exactly how it happened, but one day while I tried to shift, the chain got caught and it started to feel horrible to pedal. My rear wheel locked up and I lifted my bike to the side of the road. I saw that the chain was wedged in between the spokes and cassette really badly. I was able to yank the chain out after spinning the wheel a bit and with a lot of force, and saw that I had damaged a bunch of spokes. Those spokes eventually broke.
So, after my spoke guard broke more recently, I knew I wanted another one. I searched a little bit online and then thought to myself "what if I could design my own and 3D print it?"
Spoke guard design considerations
So, this is not a totally necessary thing, but I wanted to be able to install the spoke protector without having to remove the gear cassette, which one would normally need to do. I couldn't really study the old one much because it had broken too much, but I did a little bit of research online to see how they attach. I figured that I could maybe make one out of two halves and somehow have them snap together.
I tried to set it up so they fit together like a puzzle piece, but I couldn't figure out a good way to make it snap without making the part too thick. It had to stay thin to stay near the spokes and not rub against the cassette or chain itself while coasting. Eventually I decided to design two identical halves that attached together via zip tie. And the same zip tie that attached the halves could also fix the spoke guard to the spokes.
I put holes into the spoke guard for small zip ties to fit through.
Printing it, putting it together and installing the spoke guard
Printing was fine. I used a clear PLA that looked okay. Clear PLA always ends up looking more whitish, I guess because of all the internal voids created during the 3D printing process.
Attaching the parts was still kind of annoying. It's hard to fit a zip tie into a small area between the cassette and the spokes. It's been a while now, but I think for the first half, I put the zip tie in place and left it really loose. On the other side, I think I put a zip tie in through one of the holes. Once the first half was in place, I used needlenose pliers to grab the free end of the zip tie and feed it through the other hole. I pulled it through a bit and was able to use my fingers to finish fixing the zip tie. I then used another zip tie or two to attach the spoke guard to some spokes to stop it from spinning and from getting too close to the cassette.
How did the spoke guard work, and how's it holding up?
So installation was a little tricky at first, but I didn't have to do much adjusting afterward. It's been working pretty well overall. I do notice some noise when I'm coasting and when the bike chain is on the largest cog of the cassette. I think the disc is rubbing against the chain when it's in this position. It's not really annoying and it feels more like a reminder, like, "ahh, that spoke guard is still there".
It's been through more than a year of sun, rain and normal commuting. It's dirtier than it was before, but holding up fine otherwise. Nothing's broken, that I'm aware of and overall I'm happy with it!
Want to make your own spoke guard? You can download this to print yourself.
Here's the spoke guard design I made. It's a single file that you print twice so you can have two halves. Let me know if you have questions about it.
